function add() {
    let args = [].slice.call(arguments);
    let fn = function(){
     let fn_args = [].slice.call(arguments)
     return add.apply(null,args.concat(fn_args))
   }
  fn.toString = function(){
    return args.reduce((a,b)=>a+b)
  }
  return fn
  }
  console.log(add(1,2,3));
